Abstract: Provided is a mobile object control device configured to: recognize a surrounding situation of a mobile object; set, based on the recognized surrounding situation, a risk area in which positions of the surrounding situation are associated with risk values that are indicator values indicating degrees to which the mobile object is to avoid traveling; generate a target trajectory indicating a route along which the mobile object is to travel in the future; cause the mobile object to travel along the generated target trajectory; and set at least one observation point in each of three or more provisional trajectories branching at a specific location ahead of the mobile object, and generate the target trajectory based on the risk area and the at least one observation point.

Abstract: A driving assistance device of an embodiment includes a recognizer configured to recognize a surrounding situation of a mobile object, a determiner configured to determine, on the basis of the surrounding situation, whether to prompt a driver of the mobile object to perform a steering operation and whether there is a possibility of a risk occurring for the mobile object, and a notification controller configured to cause a speaker to output a guidance sound prompting the driver of the mobile object to perform a steering operation and a warning sound with respect to the risk on the basis of a result of the determination by the determiner, in which the notification controller causes output modes for the guidance sound and the warning sound to be different from each other.

Abstract: A driving assistance device of an embodiment includes a recognizer configured to recognize a surrounding situation of a mobile object, a determiner configured to determine, on the basis of the surrounding situation, whether to prompt a driver of the mobile object to perform a steering operation and whether there is a possibility of a risk occurring for the mobile object, and a notification controller configured to cause a speaker to output a guidance sound prompting the driver of the mobile object to perform a steering operation and a warning sound with respect to the risk on the basis of a result of the determination by the determiner, in which the notification controller causes output modes for the guidance sound and the warning sound to be different from each other.

Abstract: According to an embodiment, a driving assistance device includes a recognizer configured to recognize a surrounding situation of a mobile object, a decider configured to decide whether or not to prompt a driver of the mobile object to perform acceleration or deceleration on the basis of the surrounding situation, and a notification controller configured to cause a speaker to output a notification sound for prompting the driver of the mobile object to perform the acceleration or deceleration on the basis of a decision result. The notification sound is a notification sound obtained by continuously changing a structure of a sound.